Although a Reuters report said the audio was undated, the references made in it - to the North Korean nuclear crisis and to the Islamic State's defeat in Mosul (in July) - suggest that it was recorded recently.

Rita Katz, the director of SITE Intelligence Group, thinks the man in the clip is Baghdadi.

Katz said in a series of tweets that Baghdadi can be heard "rallying his supporters inside and outside of ISIS territory," and demanding that "lives in Mosul, Sirte, Raqqa, Ramadi and Hama not be lost in vain." She also quotes him as saying that America is "mired in huge debt and has become politically and militarily ineffective on the world stage."

According to a report in The Telegraph, Baghdadi said "the US was no longer the world's only superpower and gave North Korea's threats as evidence of American decline, as well as Russia's domination of Syrian peace talks in Kazakhstan."

A Middle East Eye report said Baghdadi "spent more than half of the clip discussing an ideological debate inside ISIS and pleaded with Syrian opposition groups to stop working with Turkey and Saudi Arabia, countries which have provided support to anti-Assad Islamist rebel groups."

On the Western media, he said, "Oh soldiers of Islam in every location, increase blow after blow, and make the media centres of the infidels, and where they wage their intellectual wars, among your targets."

(Inputs from Reuters)

VIDEO: Here's what Baghdadi's wife had to say about him.

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